The overall long term goal of this project is to elucidate the critical cellular, biochemical, and molecular events involved in corneal epithelial cell differentiation. The proposal focuses on identification of the membrane entities related to differentiation, their spatio-temporal correlation, and the regulatory inputs affecting or determining their expression. Based on observations made and experimental systems developed during a previous funding period, the following studies will be performed: (1) characterization of the biochemical properties, ontogeny and biological role of a recently identified membrane WGA-binding glycoprotein that is expressed only following stratification; (2) identification of the source of changes in lectin-binding profiles along the stratification axis and establishment of the relationship of these changes to the biogenesis of glycocalyx protein; (3) elucidation of the relationships between the temporal expression of the tissue-specific cytokeratins and the membrane-related components, as well as the role of differentiation agents, in particular retinoic acid, on the modulation of specific stages in the development of the superficial cell phenotype. The biochemical tools developed in the above studies will be employed along with a viable marker established during the previous research period.